JP2017224907A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of reducing a color shift in an optical image depending on image plane coordinates of an image pick-up device, while dividing a luminous flux into a finder optical system and the image pick-up device by use of a half mirror.SOLUTION: The imaging apparatus includes: an imaging part that captures an image by an objective with an image pickup device having a plurality of different spectral characteristics and outputs an image signal corresponding to the captured image; an optical element that can be inserted into and removed from an optical path including the objective and focus detecting means; objective condition detecting means for detecting conditions of the objective; and memory means for storing information relating to a light quantity correction amount that differs by a position within a light-receiving plane of the image pickup device, determined by the lens conditions obtained by the objective condition detecting means. The imaging apparatus corrects a captured image when the optical element is inserted by using the focus detecting means and the light quantity correction amount.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging device, and more particularly to an imaging device provided with a half mirror.

  In a single-lens reflex camera provided with a half mirror, an imaging apparatus that distributes a subject image to a finder optical system and an imaging element 4 with a half mirror is known (Patent Document 1). According to this method, since the light beam is reflected to the finder optical system by the half mirror, a bright and high-definition subject image can be observed by the finder optical system, and at the same time, AF, AE, and AWB can always be performed by the image sensor.

Japanese Patent Laid-Open No. 11-295810

  However, the half mirror actually has a spectral transmittance that is not uniform at all wavelengths. Thereby, the color of the optical image formed on the image sensor differs depending on whether or not the half mirror is in the optical path of the imaging optical system.

  Further, the light that passes through the half mirror and enters the image sensor has an incident angle that varies depending on the imaging coordinates of the image sensor. The half mirror controls the reflectance with an optical thin film. When the incident angle of the light beam changes, the length of the light beam passing through the film changes, so that the transmittance varies depending on the incident angle and wavelength, and the color of the optical image varies depending on the image plane coordinates of the image sensor. When the color deviates from the captured image, AF, AE, and AWB that perform calculation using the image have an error.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image pickup apparatus that can reduce color shift of an optical image due to image plane coordinates of an image pickup element while dividing a light beam into a finder optical system and an image pickup element with a half mirror. It is in.

In order to achieve the above object, an imaging apparatus according to the present invention includes:
An imaging unit that captures an image generated by the objective lens with an imaging device having sensitivity in a plurality of different wavelength regions, and outputs an image signal corresponding to the captured image, and the objective in the optical path of the objective lens An optical element that is rotationally asymmetric with respect to the optical axis of the lens, means for acquiring information relating to the imaging condition of the objective lens, and a light amount correction coefficient that is asymmetric with respect to the optical axis of the objective lens determined by the imaging condition And an image pickup apparatus that corrects a photographed image using the light quantity correction coefficients of a plurality of different spectra.

  According to the present invention, there is provided an imaging apparatus capable of correcting a color shift of an optical image and reducing a measurement error using the optical image while dividing a light beam into a finder optical system and an imaging element by a half mirror. Can be provided.

It is a figure which shows the form of the Example optimal for this invention. It is the figure which showed an example of the spectral transmittance of the half mirror in the Example of this invention, and its incident angle dependence. It is an example of the spectral sensitivity of the image pick-up element in the Example of this invention. It is an example of the spectral sensitivity of the image pick-up element which considered the half mirror in the Example of this invention. It is a figure which shows the relationship between the output of an image pick-up element, and an incident angle in the Example of this invention. It is a figure which shows the table of the correction value of the output of the image pick-up element in the Example of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of an imaging apparatus according to an embodiment of the present invention.

  Hereinafter, an imaging apparatus according to an embodiment of the present invention will be described with reference to FIG.

  This imaging device includes a camera device 1 and a lens device 2 including a photographic optical system 3 for forming a detachable subject light image.

  On the optical path of the imaging optical system 3 when the lens apparatus 2 is mounted, a half mirror 4 that is a movable reflection mirror such as a quick return mirror is disposed. When the light is reflected, the reflected light beam enters the finder optical system 5.

  The half mirror 4 has a transflective portion at least partially configured to transmit a part of the subject luminous flux even when it is located in the optical path.

  The finder optical system 5 includes a focusing screen 6 disposed on the focal plane of the photographing optical system 3, a pentaprism 7 for converting a subject image formed on the focusing screen 6 into an erect image, and the pentaprism. 7 and an eyepiece 8 for enlarging and projecting the image projected on the eyes of the photographer.

  At the focal plane position of the photographic optical system 3 on the optical path of the light beam transmitted through the half mirror 4 or on the optical path of the light beam when the mirror 4 is retracted from the optical path, the subject optical image is photoelectrically converted to an electric signal. As shown in FIG.

  The output of the image sensor 9 is converted into a digital signal by an A / D converter (not shown). This digital signal includes an autofocus (AF) circuit 101 serving as a focus position detecting unit for calculating the distance to the subject and determining the focus position of the imaging optical system 3, and the exposure value by calculating the luminance of the subject. An automatic exposure control (AE) circuit 102 that constitutes an exposure control means for determining the white balance value, and an auto white balance (AWB) circuit 103 that constitutes a white balance control means for calculating and determining the white balance value of the subject, Each AF is input, and the AF value, AE value, and AWB value are evaluated based on predetermined data, program lines, etc., and whether or not they are appropriate values is determined according to the result. Control is performed to cause each circuit to perform correct correction.

  That is, when it is determined that the focus position needs to be adjusted based on the AF value obtained from the AF circuit 101, the focus position is adjusted to an appropriate position by moving the focus lens.

  However, since the in-focus position is different when the spectral transmittance is different, the in-focus position is different when the image height is different.

  If it is determined that the exposure needs to be adjusted based on the AE value obtained from the AE circuit 102, an appropriate aperture amount is adjusted, and the charge accumulation time by the image sensor 9 is controlled, so-called element The shutter time of the shutter is adjusted, or the gain of the imaging signal is adjusted.

  Further, when it is determined that the white balance needs to be adjusted based on the AWB value obtained from the AWB circuit 103, the color balance is adjusted by varying the amplification factor of each color.

  At that time, the image signal of the image sensor 9 is used. If it is used as it is, it deviates from the original spectral intensity ratio due to the spectral transmittance of the half mirror 4. Then, there is a possibility that all output values of AE, AF, and AWB have an error. In order to prevent this, in this embodiment, information relating to the transmittance of the half mirror 4 is described in the imaging device 9 and the image signal information obtained from the imaging element 9 is corrected using the information. Thereby, the color shift of the image signal information due to the spectral transmittance of the half mirror 4 can be reduced.

  The specific contents are described below.

  FIG. 2 is a diagram showing an example of the incident angle dependence of the spectral transmittance of the half mirror 4.

  The light that has traveled on the optical axis of the imaging optical system 3 is incident on the half mirror at 45 °, and thus exhibits a spectral transmittance indicated by a short dotted line. Looking at this spectral transmittance, the half mirror 4 shows a substantially uniform spectral transmittance in the visible light wavelength range.

  However, in the ultraviolet and infrared regions, there is no effect on normal photographing, so the transmittance is not uniform. Further, the spectral transmittance is shown as a solid line when the incident angle is 30 °, and as a long dotted line when the incident angle is 60 °. As the incident angle increases, the transmission distance of the film increases, so that the spectral transmittance shifts to the longer wavelength side, and as the incident angle decreases, the spectral transmittance shifts to the shorter wavelength side. When the incident angle is different, the transmittance is different by 10% or more at the same wavelength in the range of 30 ° to 60 °, and the amount of transmitted light changes by about 20%.

  FIG. 3 shows an example of the spectral sensitivity of the image sensor 9.

  Here, an element having sensitivity to red, green, and blue is considered. When the image pickup device 9 and the half mirror 4 are used, the total spectral sensitivity of the two is as shown in FIG. When the spectral transmittance of the half mirror 4 changes as shown in FIG. 2 depending on the incident angle, the outputs of red, green, and blue change as shown in FIG. When the incident angle is smaller than 45 degrees, the blue output on the short wavelength side is weaker than when it is incident at 45 °, and when the incident angle is larger than 45 °, the red output on the long wavelength side is weaker than when it is incident at 45 °. The green output does not change much with the combination of the imaging element 9 and the half mirror 4 this time.

  Consider a case where a white subject is photographed. The intensity ratio of the red, green, and blue image signals at this time is a ratio of values obtained by integrating the graph of FIG. 4 with the wavelength. FIG. 5 shows the relationship between the calculated incident angle and the red, green, and blue outputs. This graph shows the relationship between the output and the incident angle when the output at the incident angle of 45 degrees is 1. The intensity of the green image signal hardly changes depending on the angle. However, as described above, when the incident angle is larger than 45 °, the blue output is small and the red is large. If the angle is less than 45 °, blue becomes large and red becomes small.

  Here, the red output when incident at 30 °, 45 °, and 60 ° respectively represents the green output when incident at R30, R45, R60, 30 °, 45 °, and 60 °, respectively G30, G45, G60, When the blue output when incident at 30 °, 45 °, and 60 ° is B30, B45, and B60, respectively, the light incident at 30 ° is red by R30 / R45 times the light incident at 45 °. Green is G30 / G45 times and Blue is B30 / B45 times. In addition, light incident at 60 ° is R60 / R45 times red, G60 / G45 red, and B60 / B45 times red compared to light incident at 45 °. In order to correct this, the respective reciprocals are multiplied. Then, the luminance values are the same as those at 45 ° incidence at all image heights. By doing so, the color difference due to the image height on the half mirror 4 can be reduced.

  The incident angle to the half mirror 4 varies depending on the imaging state such as focal length, object distance, and F value. Therefore, the camera device 1 needs to use different correction coefficients depending on the imaging state of the photographing optical system 3 and the image height. FIG. 6 shows an example of the correction coefficient. Although a correction coefficient table for each pupil distance, F value, and image height is shown here, a table for other imaging states (focal length, object distance, etc.) may be provided. When the camera device 1 and the lens device 2 communicate with each other, the camera device 1 acquires information on the imaging state (pupil distance, F value) of the imaging optical system 3. A suitable correction coefficient is selected from the acquired imaging state. For example, when the pupil distance is P1 and the image height is h1 at F2.8, the luminance value is corrected using R28_1 for red and B28_1 for blue. The table may be possessed by the lens device 2.

  Data may be possessed as a coefficient of a function of imaging information such as focal length and pupil distance and coordinates on the image sensor 9. At that time, the correction coefficient may be calculated from the coefficient of the function, the imaging state, and the coordinates on the imaging element 9 by the camera device 1 or the lens device 2.

  Further, when the camera device 2 possesses data, the camera device 2 may have information on the change in spectral transmittance due to the manufacturing error of the half mirror.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  In an imaging apparatus including a half mirror, errors in various measurements using images can be reduced.

1 camera device, 2 lens device, 3 imaging optical system, 4 half mirror,
5 Viewfinder optical system, 9 Image sensor

Claims (5)

An imaging unit that captures an image generated by the objective lens with an imaging device having sensitivity in a plurality of different wavelength regions, and outputs an image signal corresponding to the captured image;
An optical element rotationally asymmetric with respect to the optical axis of the objective lens in the optical path of the objective lens;
Means for acquiring information relating to imaging conditions of the objective lens;
Storage means for storing a light amount correction coefficient asymmetric with respect to the optical axis of the objective lens determined by the imaging conditions;
An imaging apparatus, wherein a captured image is corrected using the light amount correction coefficients of a plurality of different spectra. The imaging apparatus according to claim 1, wherein the imaging state is an exit pupil distance. The imaging apparatus according to claim 1, wherein the imaging state is an F value. The imaging apparatus according to claim 1, wherein exposure control is performed using the corrected photographed image. The imaging apparatus according to claim 1, wherein focus detection is performed using the corrected photographed image.